A 2-LAYER WIND-DRIVEN OCEAN MODEL IN A MULTIPLY CONNECTED DOMAIN WITHBOTTOM TOPOGRAPHY

The behavior of the solution to a two-layer wind-driven model in a mul tiply connected domain with bottom topography imitating the Southern O cean is described. The abyssal layer of the model is forced by interfa cial friction, crudely simulating the effect of eddies. The analysis o f the low friction regime is based on the method of characteristics. I t is found that characteristics in the upper layer are closed around A ntarctica, while those in the lower layer are blocked by solid boundar ies. The momentum input from wind in the upper layer is balanced by la teral and interfacial friction and by interfacial pressure drag. In th e lower layer the momentum input from interfacial friction and interfa cial pressure drag is balanced by topographic pressure drag. Thus, the total momentum input by the wind is balanced by upper-layer lateral f riction and by topographic pressure drag. In most of the numerical exp eriments the circulations in the two layers appear to be decoupled. Th e decoupling can be explained by the JEBAR term, whose magnitude decre ases as interfacial friction increases. The solution tends toward the barotropic one if the interfacial friction is large enough to render t he JEBAR term to be no larger than the wind stress curl term in the po tential vorticity equation. The change of regimes occurs when the valu e of the interfacial friction coefficient kappa equals kappa(0) = H(1) f(0)(L-y/L-x)(A/H-0), where f(0) is the mean value of the Coriolis par ameter; L-y and L-x are the meridional and zonal domain dimensions; H- 0 and H-1 are the mean depths of the ocean and of the upper layer; and A is the amplitude of topographic perturbations. Note that kappa(0) d oes not depend on the strength of the wind stress. The magnitude of th e total transport is found to depend crucially on the efficiency of th e momentum transfer from the upper to the lower layer, that is, on the ratio kappa/epsilon, where epsilon is the lateral friction coefficien t. If epsilon and kappa are assumed to be proportional, the upper-laye r transport and total transport vary as epsilon(-5/6).